In-flight refueling (or air-to-air refueling) is an important method for extending the range of aircraft traveling long distances over areas having no feasible landing or refueling points. Although in-flight refueling is a relatively common operation, especially for military aircraft, precise positioning of a second aircraft (the receiver aircraft, for example) with respect to a first aircraft (the tanker aircraft, for example) is required in order to provide a safe engagement of the first aircraft with the second aircraft for the dispensing of fuel. The requirement of precise relative spatial positioning of two rapidly moving aircraft, makes in-flight refueling a challenging operation.
There are currently two primary systems for in-flight refueling. One system is the boom refueling system. The boom refueling system typically comprises a rigid boom extended from a refueling aircraft. At one end of the boom is a refueling nozzle and adjacent the refueling nozzle are airfoils, which are controlled by a boom operator on the refueling aircraft. The airfoils provide maneuverability of the boom with respect to an aircraft that is to be refueled. For the aircraft that is to be refueled, the second aircraft, the operator of the second aircraft must maneuver the second aircraft to within an in-flight refueling position, below and aft of the first aircraft. Upon maneuvering into the in-flight refueling position, the boom operator controls the airfoils to position and mate the boom into a refueling connection on the second aircraft.
Another type of refueling system is the probe and drogue system. In the probe and drogue system, a refueling hose having a drogue disposed on one end is trailed behind first aircraft (the tanker aircraft). The second aircraft has a probe that is flown by its operator into the drogue. As the drogue typically moves away from the second aircraft as it approaches, great skill and maneuvering ability is required by the operator of the second aircraft to mate the probe with the drogue. It is preferable, in the probe and drogue system, for the second aircraft to approach and enter the in-flight refueling position relative to the first aircraft as in the boom system, except in this case, the operator of the second aircraft is also responsible for “flying” the second aircraft's probe directly into the trailing drogue, because the drogue lacks the control surfaces that are provided on the refueling boom.
Thus, for both types of in-flight refueling systems, the operator of the second aircraft must maneuver the second aircraft to the in-flight refueling position (IFRP) and maintain the second aircraft's position in the IFRP relative to the first aircraft for the duration of the fueling operation. The approach and positioning of the second aircraft must be precise in order to avoid potentially dangerous areas of air turbulence that may be created in the wake of the first aircraft by, for instance, the first aircraft's engines and control surfaces. To avoid areas of potential turbulence, the second aircraft, in many cases, approaches the first aircraft from the aft and from below so that it intercepts the IFRP as described more fully herein. Thus, a positioning system for guiding a second aircraft to the IFRP relative to a first aircraft is needed.
Optical systems have been disclosed for positioning refueling drogues with respect to refueling probes attached to receiver aircraft. As refueling drogues, however, have proven relatively unmaneuverable, these systems have not been operationally viable. One such optical system is described in U.S. Pat. No. 5,326,052 to Krispin et al. Other optical systems for positioning objects with respect to reflectors and retro-reflectors have not been easily adapted for use in all types of in-flight refueling systems. In addition, optical landing aids, such as visual approach slope indicator (VASI) systems, are useful for providing optical glide slope information for aircraft approaching a fixed runway, however such systems have not yet been successfully adapted to position two moving objects relative to each other. Also, radio-signal positioning systems, such as the instrument landing system (ILS), provide radio signals to laterally position aircraft approaching a fixed runway along a suitable approach glide slope, but such systems are also not tailored for use in situations where the positioning device is located on a moving aircraft, nor where an upward glide slope is required to guide a second aircraft up and forward into the IFRP relative to a first aircraft (such as a tanker aircraft).
Therefore, there exists a need for an in-flight refueling positioning system that provides a positioning device to guide a second aircraft into the in-flight refueling position with respect to a first aircraft. This need extends to in-flight refueling operations using both a boom in-flight refueling system and a probe and drogue in-flight refueling system. There also exists a need for a positioning system that is compatible with receiver devices sometimes installed in the second aircraft and using a signal that may be recognizable by an operator of the second aircraft. There also exists a need for an in-flight refueling positioning system that is functional in an in-flight refueling operation taking place at night or in inclement weather.